emWin: LCD1781 driver

Supported hardware

Controllers

This driver has been tested with the following LCD controllers

Solomon SSD1781
Solomon SSD1783

Bits per pixel

Supported color depth is 16 bpp.

Interfaces

The driver supports 8-bit parallel (simple bus) or 4 pin SPI interface.

Display data RAM organization

The picture above shows the relation between the display memory and the SEG and COM lines of the LCD. The display memory is divided into two panes for each pixel. The lower bit of one pixel is stored in pane 0 and the higher bit is stored in pane 1.

Additional RAM requirements of the driver

This LCD driver may be used with or without a display data cache, containing a complete copy of the contents of the LCD data RAM. If a cache is not used, there are no additional RAM requirements. The amount of memory used by the cache is: LCD_XSIZE x LCD_YSIZE x 2 bytes.

Additional driver functions

None.

Hardware configuration

This driver accesses the hardware with a simple bus interface or a 4 pin SPI interface as described in Chapter 26: "Low-Level Configuration". The following table lists the macros which must be defined for hardware access:

Parallel mode

Macro	Explanation
LCD_INIT_CONTROLLER	Initialization sequence for the LCD controller.
LCD_READ_A1	Read a byte from LCD controller with A-line high. (Used only if working without cache)
LCD_WRITE_A0	Write a byte to LCD controller with A-line low.
LCD_WRITE_A1	Write a byte to LCD controller with A-line high.
LCD_WRITEM_A1	Write multiple bytes to LCD controller with A-line high.

Display Orientation

The controller SSD1781 supports rotating and mirroring. So it is recommended to use the hardware functions of the controller if rotating and/or mirroring is needed instead of the display orientation macros LCD_MIRROR_... and LCD_SWAP_XY of emWin. The configuration sample folder contains a sample which uses the hardware to rotate the output 180 degrees. The command 0xBC of the controller can be used to mirror and/or rotate the display output. For more details about how to change the display orientation via the hardware functions please refer to the manual of the SSD1781.

Additional configuration switches

The following table shows optional configuration switches available for this driver:

Macro	Explanation
LCD_FIRSTCOM0	This macro can be used to define the first common address to be used in the data RAM of the display controller. The value can be determined experimentally or taken from the display documentation.
LCD_FIRSTSEG0	This macro can be used to define the first segment address to be used in the data RAM of the display controller. The value can be determined experimentally or taken from the display documentation.
LCD_GET_BUSY	The SSD1781 controller has a separate pin which should be used to query the busy state. This macro should return 1 if the busy line of the SSD1781 is high and 0 if the line is low. If the macro is defined it is used at the beginning of each low level driver function to wait until the driver is not busy. Example: #define LCD_GET_BUSY() (P6 & 0x80)
LCD_WAIT	If the busy line is not available the macro LCD_WAIT can be used to call a function which waits a while in dependence of the number of drawn pixels. If defined the LCD_WAIT macro is executed after each high level drawing function call of the SSD1781. Example: #define LCD_WAIT(NumPixels) OS_Delay((NumPixels + 900) / 1000)

Special requirements for certain LCD controllers

The driver needs to work in the fixed palette mode 565. The driver does not work with other palettes. Further the driver needs to swap the red and the blue part of the color index. You should use the following macro definitions in the file LCDConf.h:
#define LCD_SWAP_RB 1